The present invention relates to a vibration damping apparatus for damping vibration of a structure such as a building or a tower due to wind or earthquake, vibration of piping due to pump operation or pulses, or vibration of equipment due to motor operation and, more particularly, to a self-tuning type vibration damping apparatus for damping vibration of a vibration damping target by utilizing the motion of a sphere tuned to vibration of the target.
A huge structure such as a building, a bridge, or a tower is flexible and readily vibrates. Vibration is excited by a wind external force. A large vibration may break the structure to result in a serious problem. The followings are conventional vibration damping apparatuses as measures against vibration.
(Measure 1)
As shown in FIG. 1, a vibration damping apparatus (this apparatus is called a dynamic vibration damper) comprising a mass 10, a spring 13, and an oil damper 12 is attached on the top of a building 1 (or in the building near the top). The frequency is tuned to the natural frequency of the building 1, thereby reducing vibration.
(Measure 2)
As shown in FIG. 2, an actuator 14 is attached on the top of a building 1, and a mass 10 is driven by the actuator 14, thereby actively reducing vibration.
(Measure 3)
For, e.g., piping, which vibrates due to pump operation or pulses, a support 15 extending from a header pipe 6 is conventionally arranged to damp large vibration of piping 8, as shown in FIG. 3.
(Measure 4)
For, e.g., piping, a fixing table 17 is arranged and coupled to piping 8 through an oil damper 12, as shown in FIG. 4.
(Measure 5)
Like a building, piping can also employ a dynamic vibration damper comprising a mass 10 and a flat spring 18, in which a vibration element of a single-degree-of-freedom system having a frequency equal to that of piping 8 is attached and resonated to reduce vibration of the piping, as shown in FIG. 5.
(Measure 6)
A vibration damping apparatus comprising a mass 10 suspended from a coil spring 13, and a sphere 5 inserted into a groove 20 formed in the mass 10, as shown in FIG. 6, has also been developed as a vibration damping apparatus for a columnar structure. In case of small vibration, the sphere 5 collides against a columnar structure 19. In case of large vibration, the sphere 5 collides against the mass 10 and the columnar structure 19. The vibration energy is transformed to a collision energy, so that the vibration is reduced.
However, the conventional vibration damping apparatuses have the following problems.
(Problem of Measure 1)
To obtain a predetermined vibration damping effect, a vibration damping apparatus comprising a large mass whose frequency is adjusted, a spring, and an oil damper is required, and optimally adjusting the frequency is labor- and cost-intensive. Especially, the spring and oil damper are expensive.
(Problem of Measure 2)
The actuator must actuate a large mass and therefore requires a large energy, resulting in a problem of cost.
(Problem of Measure 3)
To set the support 15, a support attachment band 16 for supporting the support 15 must be arranged, so this apparatus can hardly be set at a portion where a plurality of pipes are complexly arranged.
(Problem of Measure 4)
The oil damper 12 for vibration damping is expensive. In addition, to set the oil damper 12, the fixing table 17 is necessary. In fact, it is difficult to set the oil damper 12. For high-temperature piping, the oil damper 12 can hardly be set because the damper characteristics change with temperature.
(Problem of Measure 5)
Like the vibration damping measure (measure 1) for a building, the frequency must be tuned to that of the target piping 8. The dynamic vibration damper must be designed, manufactured, and adjusted on the basis of the frequency of the piping 8 which is measured in advance.
(Problem of Measure 6)
Since this apparatus is an impulse type vibration damping apparatus, the vibration damping effect is poorer than that of the dynamic vibration damper (measure 1 or 5) for an identical mass ratio (mass of the vibration damping apparatus/weight of the target structure). In addition, wear or impulse sound on the collision surface of the sphere 5 or the mass 10 poses a problem.